This invention relates generally to hot runner injection molding and more particularly to injection molding apparatus having a removable nozzle seal which screws onto the outside of the front end of the heated nozzle.
Nozzle seals bridging the insulative air space between the heated nozzle and the surrounding cooled mold are well known. U.S. Pat. No. 4,793,795 to Schmidt et al. which issued Dec. 27, 1988 shows a gate insert which screws into place and U.S. Pat. No. 5,028,227 to Gellert et al. which issued Jul. 2, 1991 shows a gate insert which slides into place. U.S. Pat. No. 5,299,928 to Gellert which issued Apr. 5, 1994 shows a two-piece nozzle seal which screws into place. U.S. Pat. No. 5,849,343 to Gellert et al. which issued Dec. 15, 1998 shows another type of gate insert which screws into place. While these previous nozzle seals and gate inserts are suitable for many applications, they all have the disadvantage that they are seated in an opening on the inside of the nozzle. This limits the size of any insert or liner seated in the front end of the nozzle which, in turn, restricts the strength and thermal conductivity from the heating element to the gate. The ones that screw in have the further disadvantage that location of the front end of the nozzle is not accurate enough for some applications.
It is also known to provide a sealing ring extending around the outside of the nozzle. For instance, U.S. Pat. No. 5,795,599 to Gellert which issued Aug. 18, 1998 shows a nozzle guide and sealing ring mounted around the outside of the front end of the nozzle.